Abstract
Purpose:
The optic nerve lamina (ONL) is a unique optic nerve structure that borders the retina and optic nerve. The ONL is believed to play an important role in many optic nerve diseases, including nonarteritic anterior ischemic optic neuropathy (NAION) and open angle glaucoma (OAG). We recently demonstrated that some cells in the ONL possess the ability to develop into a number of different cell types, suggesting pluripotency. We utilized a panel of gene-specific primers to examine both the pluripotency and types of cell differentiation in this region, and evaluated the relative changes in gene expression in different age group.
Methods:
10 wild type mice (C57BL/6J) each at 15 day, 6 months and >1year old were utilized for the analysis. The first two mm of the optic nerve head was utilized for the ONL, as well as tissue from the retina and posterior ON (posterior 3mm of optic nerve). mRNA was extracted using Qiagen RNaeasy Micro kit, and unbiased linear RNA amplification using a single chimeric primer and isothermal amplification (Nugen) was performed, to enable sufficient material for multiple assays. Following cDNA generation, we performed quantitative PCR (qPCR). A variety of gene markers were used including Nestin, Sox2, and Sox1 for progenitor cells, as well as a number of genes for each glial cell type and glial progenitor line. Reactions were performed using SYBR green Super mix on an iCycler.
Results:
qPCR revealed differential gene expression between the lamina and optic nerve, as well as between the different age groups. Gli-1, Nestin and SOX-2 gene expression were considerably elevated in the lamina and ON, compared with the retina. In contrast, the highest levels of Olig-2 and MBP gene products, corresponding to mature oligodendrocytes, were found in the posterior ON region. High levels of GFAP and s100β expression were detected in posterior ON, less in the lamina, and minimal levels expressed in the retina.
Conclusions:
The ONL is a progenitor cell niche, whose capacity for self-renewal declines during aging. ONL gene expression is distinct from either the retina or ON. Our results suggest that the ONL lamina region possesses a multi-progenitor cell population that may give rise to the different glial cell lines, as well as possess some capacity for neuronal generation.
Keywords: 533 gene/expression •
721 stem cells •
629 optic nerve